1. Field of the Invention
The invention relates to an insulation-displacement terminal fitting.
2. Description of the Related Art
A known insulation-displacement terminal fitting includes opposed side walls and a wire-receiving space between the side walls, as disclosed in Japanese Examined Patent Publication No. 57-10550. Opposed V-shaped insulation-displacement portions are press-formed to project from the respective side walls and into the wire-receiving space. The insulation-displacement terminal fitting is used with a wire that can be pushed transversely into the wire-receiving space. As a result, the insulation-displacement portions cut through a resin coating of the wire and contact a core of the wire at the cut-open sections of the resin coating.
The V-shaped insulation-displacement portions in the side walls of the conventional insulation-displacement terminal fitting are thinned and elongated during their press-formation. However, excessive elongation may reduce the strength of the insulation-displacement portions. Furthermore, there are limits to the projecting distances of the insulation-displacement portions from the side walls.
In view of the above, it is an object of the present invention to provide an insulation-displacement terminal fitting with insulation-displacement portions that are not thinned and elongated excessively.
The invention is directed to an insulation-displacement terminal fitting with opposed side walls and a wire receiving space between the side walls. Insulation-displacement portions are cantilevered from the side walls and project into the wire-receiving space. The insulation-displacement portions each have a base end at the respective side wall, a projecting end in the wire receiving space and an intermediate bend between the base end and the projecting end. The intermediate bends of the insulation-displacement portions cut the resin coating on a wire that is pushed transversely into the wire receiving space. Further pushing of the wire brings the intermediate bends of the respective insulation-displacement portions into contact with the core of the wire at the cut-open sections of the resin coating.
The insulation-displacement portions are formed by making cuts in the side walls and folding the cut portions inwardly. The intermediate bends are formed by bending an intermediate portion of each cantilevered insulation-displacement portion back toward the corresponding side walls.
Openings are made in the side walls by the cutting, folding and bending that forms the insulation-displacement portions, and the insulation-displacement portions extend from edges of the respective openings. Each insulation-displacement portion is folded away from the respective opening and then is bent back toward the inner surface of the respective side wall. Insertion of the wire into the wire-receiving space creates forces on the insulation-displacement portions that tends to urge the insulation-displacement portions outwardly and away from the wire-receiving space. Accordingly, the space between opposed insulation-displacement portions could be increased, and the effectiveness of the contact between the insulation-displacement portions and the core of the wire could be reduced. However, such outward displacement of the insulation-displacements portion during insertion of the wire is restricted by contact between the extending ends of the insulation-displacement portions and the inner surface of the respective side wall. Accordingly, a reliable contact and a specified contact pressure with the core of the wire can be achieved.
Forces created during insertion of the wire into the wire-receiving space also tend to flatten the intermediate bends. Such flattening could increase the distance between opposed intermediate bends, and hence could reduce the effectiveness of the contact between the insulation-displacement portions and the core of the wire. To prevent such reduced effectiveness, the side walls of the insulation-displacement terminal of the subject invention may be formed with stoppers. The stoppers are disposed to engage the extending ends of the insulation-displacement portions. Thus, the stoppers restrict flattening of the intermediate bends and substantially prevent associated displacements of the extending ends of the insulation-displacement portions in directions parallel to the side walls. Accordingly, the distance between opposed insulation-displacement portions remains substantially constant during insertion of the wire into the wire receiving space.
Insulation-displacement portions may be formed in two positions on each side wall, such that the insulation-displacement portions on each side wall are spaced apart in the longitudinal direction of the wire. The two insulation-displacement portions on each side wall preferably extend in opposite directions with respect to the longitudinal direction of the wire.
The insulation-displacement portions are cantilevered from the side walls, and therefore are not thinned and elongated like conventional insulation-displacement portions that have opposite ends supported on side walls.
Additionally, the insulation-displacement portions will not be displaced in directions away from the wire. Therefore, a specified contact pressure can be secured between the insulation-displacement portions and the wire.
Furthermore, the stoppers restrict flattening of the insulation-displacement portions. Hence, the projecting distances of the insulation-displacement portions from the side walls are not reduced, and a specified contact pressure can be achieved between the insulation-displacement portions and the wire.